Today ultrasonics, X-ray, computer tomography (also known as "CT scan"), and other imaging technologies are used to visualize and localize pathological changes, e.g. tumors, within a patient's body. X-ray and ultrasonics have limited use in visualizing and localizing such tumors because the body constitution of the patient often hides the suspected pathological change and because small changes cannot be detected. Computer tomography does not have these limitations.
Once a suspected pathological change has been located with a visualization apparatus such as CT scan, it is necessary to retrieve a tissue sample of the suspected tumor for biopsy. Tissue samples are commonly obtained by puncturing the skin of the patient with a biopsy needle, guiding the needle to the site of the suspected tumor, and withdrawing a sample of the tissue. Punctures in the thorax, abdomen and pelvis are conventionally performed by hand after suitable localization of the pathological change. Vertically performed punctures are usually relatively simple to accomplish and provide a relatively high frequency of acceptable tissue specimens, while punctures performed by hand which require an angling of the puncture needle cannot be performed without difficulty and give a lower frequency of successful results. Furthermore, when retrieving tissue samples of small pathological changes, it is very difficult, if not impossible, to hit the target tissue or organ when guiding the needle by hand.
Thus, there is a need for an apparatus which permits accurate and easy retrieval of acceptable tissue specimens from locations within the body of a patient which require angling of the needle to reach the target tissue.
There is a further need for an apparatus which permits accurate and easy retrieval of tissue speciments from small pathological changes.
Various instruments are known for assisting in guiding biopsy needles to a location identified by computer tomography. One such puncture instrument comprises a needle guide which can be angled and is mounted on a stand arranged on the patient table. The stand is vertically and horizontally adjustable relative to the patient table, and the needle guide is either displaceably mounted on the stand or the stand is displaceably mounted to the patient table. Adjustments can be made in x-, y- and z-directions, and the needle guide can be angled 0.degree.-180.degree.. With this instrument, however, repeated attempts are often necessary to obtain an acceptable specimen from the target tissue. Such repeated efforts are time consuming, increase the expense of the procedure, and are painful for the patient in cases where local anesthetic cannot be administered. Furthermore, where multiple attempts are necessary to retrieve a satisfactory tissue sample, additional CT images are required to check needle placement, exposing the patient to further radiation and tying up the CT table for extended periods of time. Also, known prior art guidance devices cannot be brought with the patient into the tomograph to check the position of the needle.
Thus, there is a need for an apparatus which provides increased accuracy of needle placement, thereby reducing the duration of the procedure and minimizing the radiation to which the patient is exposed.
There is also a need for an apparatus which can shorten the time required to retrieve a tissue sample and thereby reduce the expense and discomfort associated with the procedure.
There is a further need for an apparatus which can be introduced into the tomograph with the patient to verify correct location of the biopsy needle with respect to the target tissue.
Yet another disadvantage of known prior art guidance devices is that while such devices are capable of directing the biopsy needle along a desired path, they do not control the location of the needle along that path, that is, the devices do not control the depth of penetration of the biopsy needle. Thus, it is possible for the biopsy needle to be directed along the proper path but for the needle tip to be directed to a location either proximal or distal to the target tissue. Not only can improper penetration depth result in failure to direct the biopsy needle to the target tissue to obtain a tissue specimen, but also accidental overpenetration can result in laceration or perforation of organs or vessels lying distal to the target tissue.
Thus, there is a need for an apparatus which not only directs the biopsy needle along the desired path but also controls the depth of penetration of the needle to prevent accidental overpenetration of the needle.
Still further problems arise with known prior art guidance devices when the skin entry point and the target tissue do not lie in the same axial slice. Known prior art guidance devices are limited to directing the needle in an axial plane, that is, in a plane normal to the longitudinal axis of the patient. Thus, where the optimum needle path lies in a plane which is oblique to the longitudinal axis of the patient, the guidance device cannot be used. The physician must resort to guidance of the biopsy needle by hand, with the attendant problems and disadvantages previously discussed.
Thus, there is a need for a guidance device which is not limited to directing a biopsy needle along a path which lies in a plane normal to the longitudinal axis of the patient.